In general, a producing oil well is subject to emulsion or paraffin build up, the build up of scale within the tubing, and corrosion. Without treatment these conditions can reduce or stop production.
In a typical oil well, oil is pumped upwardly through a central tube by the down hole pump and the tube is surrounded by a casing. Gas typically travels upwardly through the casing. Oil and gas enter the tubing and casing through perforations. Perforations are subject to plugging and the pump and tubing are subject to the build up of scale and damage by corrosion.
In the case of paraffin build up, it is a common industry practice to periodically treat the well with hot oil, trucked to the site. The truck pumps hot oil down the casing and back up the tubing. This process removes deposits of paraffin by melting the paraffin. A triplex injection truck is also used to treat down hole corrosion and scale problems. The truck batch treats the well by pumping chemicals down the casing and back up the tubing using typically three or four barrels of water to flush the chemicals down the casing. The truck must inject several gallons of chemicals per treatment to have the desired effect.
Clearly, it would be preferable to provide a continuous method for treating the well on site without the necessity of trucking in either hot oil or chemicals, on a periodic basis. Continuous treatment then would eliminate build up of emulsions or paraffin because they would never form and provide for uninterrupted production. The cost of trucking also then would be eliminated as well as the need for a periodic shut down of production for well treatment.
In U.S Pat. No. 1,645,686 there is described a device for injecting chemicals into a well. The device includes a reservoir and a collection tank and gas from the well is used to provide head pressure within the reservoir so that the chemicals will flow into the well by gravity. In U.S. Pat. No. 1,758,376 chemicals are injected into the casing down a separate pipe and head pressure is provided by a pump. Neither patent however has a provision for eliminating clogging, and both involve substantial equipment such as additional tanks or an extra run of tubing extending down the casing.